This is an investigator-conceived, -written, and -implemented protocol. An RO1 application to support this study was submitted by the Principal Investigator. Dr. Marshall had approval from the FDA to move forward with this study. Discovery Laboratories then licensed the technology for this orphan drug, and Dr. Marshall brought his NIH application to the company, who agreed to support the project. To date, two groups of normal volunteers have been studied. The first group of 10 received tyloxapol for 14 days in a dose-escalating fashion, starting at 0.125% and escalating to 5.0%. A non-productive cough developed in three subjects. The maximum dose was then decreased to 2.5%. One subject developed a cough on this dose. The cough resolved upon discontinuation of the drug. Ten additional normal volunteers were then tested at lower doses of tyloxapol and for longer periods of time. These doses were well-tolerated. In both groups of normal volunteers, no clinically significant laboratory abnormalities developed. The next phase of this investigation, namely testing the drug on patients with cystic fibrosis, has just gotten under way.